System and method for filtering electromagnetic transmissions

ABSTRACT

A combination of filters for filtering selected wavelengths of electromagnetic radiation is provided on a transparent substrate such as a plastic film or glazing of a window. The combination of filters prevents or attenuates the passage of wavelengths through the substrate into a building, where the passage of the wavelengths into the building could adversely affect people or machinery within the building. The combination of filters is useful improve wireless networks performance by blocking or attenuating undesired electromagnetic interference, and radio frequency interference.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation in part to pending U.S.application Ser. No. 10/445,942 (U.S. Patent Application Publication No.2003-0232181), filed on May 28, 2003 and entitled System And Methods ForFiltering Electromagnetic Visual, And Minimizing Acoustic Transmissions.

STATEMENT REGARDING SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO SEQUENCE LISTING

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system and method for filteringelectromagnetic and visual transmissions, and for minimizing acoustictransmissions for security purposes. More specifically, the inventionprovides a system and method to prevent unauthorized data collection andinformation exchange from or within buildings (such as through windows,doorways, other fenestration, or openings) or otherwise prevent suchunauthorized data collection and information exchange from, for example,computer monitors or screens, personal digital assistants, and localarea networks.

2. Discussion of Related Art

Electromagnetic radiation of various frequencies is radiated from manydevices used in a wide range of facilities including homes, workplacessuch as offices, manufacturing and military installations, ships,aircraft and other structures. Examples of such devices includecomputers, computer monitors, computer keyboards, radio equipment,communication devices, etc. If this radiation escapes from the facility,it can be intercepted and analyzed for the purpose of deciphering dataassociated with or encoded in the escaped radiation. For example,technology exists for reconstructing the image appearing on a computermonitor in a building from a remote location outside the building orfrom a location within a building by detecting certain wavelengthfrequencies from the monitor screen even if the monitor screen is not inview from the remote location. This is accomplished by known techniqueswherein certain frequencies of light from the monitor screen, even afterbeing reflected from various surfaces inside the building or room wherethe monitor is located, escape and are intercepted and analyzed by aneavesdropper in another location outside the building or room where themonitor is located. Obviously, the ability of an eavesdropper tointercept such radiation constitutes a significant security risk, whichis desirably eliminated from facilities where secrecy is essential.

Although walls, such as brick, masonry block or stone walls mayeffectively prevent the escape of light frequencies from a facility,radio frequencies pass through walls that are not properly grounded toprevent such passage. Moreover, windows or other openings allow thepassage of radiation to the outside where it can be intercepted, andpermit entry of various forms of radiation, such as laser beams,infrared, and radio frequencies, into the facility. As a result,sensitive or secret data may be gathered from within the structure.

Indeed, the United States Government has long been concerned by the factthat electronic equipment, such as computers, printers, and electronictypewriters, give off electronic emanations. The TEMPEST (an acronym forTransient Electromagnetic Pulse Emanation Standard) program was createdto introduce standards that would reduce the chances of leakage ofemanations from devices used to process, transmit, or store sensitiveinformation. This is typically done by either designing the electronicequipment to reduce or eliminate transient emanations, or by shieldingthe equipment (or sometimes a room or entire building) with copper orother conductive materials. Both alternatives can be extremelyexpensive.

The elimination of windows and other openings from a structure wouldobviously minimize the above-noted security risk. The disadvantages of awindowless or enclosed structure, however, are self-evident. It would behighly desirable, therefore, to prevent the escape of radiationassociated with data through windows, doorways, or other openings whileallowing other radiation to pass there-through so that the enjoyment ofthe visual effects provided by such openings can be obtained without anundue security risk.

In addition to the security risks associated with the passage of certainwavelengths of electromagnetic radiation, acoustic transmission througha window, door or other opening also poses a security risk. It would beof additional benefit if transmission of both acoustic and theaforementioned electromagnetic radiation through openings could beminimized or avoided while preserving the visual benefits providedthereby.

The need for reducing the undesirable effects of the sun—its heat,excessive energy usage, glare, and ultraviolet (UV) radiation—has led tothe development of solar control window films. Solar control windowfilms are thin polyester sheets, which are mounted on the glass windowsof buildings and automobiles via an adhesive. It is said that such filmsare effective in providing comfort, visibility, and increased energyefficiency.

In the current workplace or home environment, however, there is a needfor more protection than solar control films can provide. For example,it is important to protect the work product of an individual, business,or other entity from unauthorized data collection through the glasswindows or other openings of their offices. The conventional solarcontrol films described above are, for the most part, incapable ofrejecting the wide range of frequencies used for such unauthorized dataand information exchange.

Given the importance of security in today's competitive marketplace, asystem that could preserve the privacy of the workplace is verydesirable. Such a system would provide both comfort and security, whichin turn can bring about many benefits, including increased productivityand the preservation of confidentiality in both the public and privatesectors.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a system and method forfiltering electromagnetic, visual, and minimizing acoustic transmissionsby using a combination of filters which substantially obviates one ormore of the problems due to the limitations and disadvantages of therelated art. The invention further provides a system and methods wherebya combination of films has a shielding effectiveness which attenuatesthe transmission of radio frequency wavelengths there-through andprovides effective filtering of UV and IR light with good visible lighttransmission (VLT) without undesirable color characteristics.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the systemand methods of the present invention include a combination ofelectromagnetic radiation filters, such as selective radiation absorbersand/or selective radiation reflectors. These may be part of a window.The system and methods according to the invention have, however,non-exclusionary applications; the invention can be interposed betweenglass surfaces or applied to every type of glazing. The system andmethods according to the invention can also be used for free standingproduct application for computer screens, monitors and other stand-alonedevices. Further, the system and methods according to the invention maybe configured to form a separate covering, which may be placed overcomputer screens, monitors and other stand-alone devices. The example ofwindows discussed herein is employed for convenience and is not intendedto be limiting as to surface application.

The radiation filters of the combination may be individual or combinedlayers plied to a window in any sequence so that light, which passesthrough the window, passes through the radiation filters used in thecombination. The radiation filters may be applied on any surface of theglazing (i.e., glass or other transparent material used for windows) ofthe window to form a multilayered structure of the filters on theglazing. It is not essential for all the layers to be contiguous to eachother on one surface of the glazing. Instead, the filters may bedistributed in any manner over or in the glazing of a window so as toprevent the passage of the wavelengths which would pose a security riskif they were allowed to pass through the window. For example, one filtermay be on one surface of a glass pane while the remaining filters may bedistributed as a single or multilayer structure on another surface ofthe glass layer (e.g., glass pane) or the filters may be distributed onany of the surfaces of a plurality of glass layers of a window (e.g., amulti-glazed window structure such as a double or triple glazed windowstructure).

In addition, any or all of the filters may be used in conjunction with aconventional glass interlayer such as the glass interlayer used inconventional safety glass which comprises a plastic interlayer such aspolyvinylbutyral (PVB) interposed between two glass layers. The filtersmay be incorporated in, deposited on, or laminated to or within theinterlayer in which case the filters will be within the glazing of thewindow.

Each filter of the combination of filters is advantageously in the formof an individual layer or coating, but this is not essential. In thecase of filters which are absorbers (filters which use a particular dye,metal, metal salt or pigment to absorb a desired wavelength or range ofwavelengths), the entire combination of absorbers or a portion of thecombination may be in the form of a mixture of dyes, metal, metal saltor pigments in a single layer as a coating or may be incorporated in acomponent of the window such as in the polyvinylbutyral interlayer usedin safety glass or in an adhesive layer used to adhere film, sheets orthe like to the glass. It is also possible to incorporate one or more ofthe absorbers as a mixture in a film or sheet attached to the window oras layers applied to or coated onto a film or sheet. The PVB layer orthe adhesive layer may include electrically conductive particles thereinin an amount to render the PVB or the adhesive conductive.

The film or sheet may be any of the films or sheets used to makeconventional solar control films. An example of a film used for thispurpose includes, polyethylene terephthalate (PET), but others may beused as well.

When a film or sheet is used in combination with glass, it is notessential for the entire combination of filters to be in or on the filmor sheet. For example, one or more filters may be associated with thefilm or sheet as described above while any remaining filters may beconnected to the glass as described above or vice versa. It is alsopossible to include a layer which comprises a mixture of absorbers withanother layer which is a different filter to make the desiredcombination. For example, two absorbers such as dyes or pigments of thecombination may be used as a mixture as two filters of the combination,and another filter of the combination may be in the form of a distinctlayer or coating such as a metal reflecting or absorbing layer.

Moreover, it is not essential for the entire combination of filters tobe distributed on the same surface. For example, one or more of thefilters may be applied to the glazing of a window while remainingfilters may be applied to computer screens or monitors, personal digitalassistants, or other stand-alone devices.

It is also not essential for the combination of filters to be attachedto a surface of a window, computer screen or monitor, personal digitalassistant or other stand-alone device. For example, the combination offilters may be configured to form a separate covering, which may be softand pliable, such as a bag. In this embodiment the combination offilters may be advantageously attached to a clear or transparentflexible substrate (e.g., PET sheet or film) which may be configuredinto the shape of a bag. When configured as a separate covering such asa bag, the combination of filters may be placed over computer screens ormonitors, personal digital assistants, or other stand-alone devices, maybe easily used and removed, and preferably may be disposable.Alternatively, the separate covering may be in the form of a tent orsheet, thereby covering an entire workstation, such as an outdoor ormobile workstation.

Any coatings, layers, films, sheets, lamina or the like used in thisinvention may be applied to a component of the window (e., the glass orinterlayer component) by techniques which are conventional and wellknown to those skilled in the art. For example, metal layers may beapplied by conventional sputtering techniques or evaporative coatingstechniques. Any of the various layers may be adhered to the glass bymeans of conventional adhesives.

Although glass is described herein as the typical material which is usedto make a window, it is to be understood that other clear or transparentmaterials which are useful for making windows may be substituted for theglass. For example hard plastics such as polycarbonate, plexiglass,acrylic plastic, etc., may be used as a substitute for the glass.

In view of the above, it will be appreciated by one skilled in the artthat the required combination of filters may be associated with thewindow in any manner or sequence providing they are configured toprevent passage of the critical wavelengths there-through for achievingthe above-described security feature. Optionally additional conventionalcomponents or layers may be applied to the window to improve theaesthetics and/or visual characteristics of the window or to provideadditional solar control, anti-reflection or radiant heat exclusion orsafety and security characteristics in accordance with known techniques.

The desired effect of the present invention (i.e., filtering the passageof certain wavelengths through the window) can be achieved with any typeof light filter or light valve which prevents the passage of theselected wavelengths. Thus, for example, the light filters or lightvalves used in this invention may be any of the absorbers describedabove or any other type of light filter or light valve such as awavelength selective reflective layer or any combination of differenttypes of light filters and light valves. For example, light absorbersmay be combined with reflective layers.

It will be appreciated that the filters used in this invention areselective with respect to the wavelengths being filtered and thus theglazing remains sufficiently transparent for use as a window. Sufficienttransparency is achieved by allowing visible light transmission of atleast 1%, although higher visible light transmission of at least about25-30% is preferred, with 50%-70% being more preferred.

The combination of filters are advantageously connected to a transparentsubstrate and are configured so as to exclude the passage of theselected wavelengths there-through, such as by absorption and/orreflection of the selected wavelengths. Thus, uncoated or exposed areas,which would permit the passage of the selected wavelengths, should beavoided.

Although the filters are connected to the substrate, each filter doesnot have to be directly connected to the substrate. In other words, theconnection of a filter layer may be made by connecting the filter layerto another filter layer which was previously connected to the substrateso that one filter layer is connected to the substrate via anotherfilter layer. For example, when two filter layers are located on oneside of the substrate, one filter layer is directly connected to thesubstrate while the other filter layer is connected to the substrate viathe first filter layer (i.e., indirectly connected). The same applies ininstances where more than two filter layers are connected to one side ofthe substrate. In other words, being connected to the substrate in thisinvention is intended to cover both direct and indirect connections.Also, when a filter is formed by mixing or impregnating absorbents suchas dyes or pigments into a component, the filter comprised of dye and/orpigment is considered in the context of this invention as beingconnected to the component.

Instead of coating the filter as a layer on the substrate, the filtermay be connected to the substrate by a lamination process wherein apreviously formed filter layer is laminated onto the substrate eitherdirectly or indirectly.

The substrate may be the glazing of the window or may be a flexibletransparent sheet (e.g., plastic sheets such as PET) which is thenconnected to the glazing. A portion of the combination of filters may beconnected to the glazing and another portion of the combination offilters may be connected to one or more flexible transparent sheets,which are connected to the glazing. Alternatively the flexibletransparent substrate with the combination of filters attached theretomay be configured as a bag to contain a computer screen or monitor,personal digital assistant or other stand alone device placed therein.Preferably the bag is sealed or tightly closed with the computer screenor monitor, digital assistant or other stand alone device therein sothat the wavelengths to be filtered will not escape from the bag. Theflexible substrate with the combination of filters attached thereto mayalso be configured as a tent for temporary field applications so thatpersonnel and the computer screen or monitor, etc., may be inside thetent. In use the tent should cover the personnel and equipment inside toprevent leakage of the wavelengths which are to be filtered.

All of the filters do not have to be applied to a single substrate. Forexample, in a multi-glazed window, the combination of filters may bedistributed on one or more of the glass sheets of the glazing either asa coating or layer on the glass and on one or more sheets connected tothe glass.

At least one of the filters may be advantageously electricallyconductive to inhibit the passage of radio waves through the window.

The substrate may include other conventional solar control elements suchas light absorbing layers, anti-reflecting layers, or reflectorsthereon.

The system and method may also be used as a Glass-fragmentation SafetyFilm and, as such, may be used to minimize flying glass fragments inreal world situations. To accomplish this objective the flexible sheetmay include one or more layers which inhibit glass fragments frombecoming dangerous flying projectiles when the window breaks due toexplosion, implosion, or due to force from a projectile. A suitablelayer for this purpose is polyester film (e.g., PET) or other flexibleclear film. For example a 7 mil thick PET film is adequate for thispurpose. The PET film may be adhered to the film containing thecombination of filters with an adhesive (e.g., a pressure sensitiveadhesive such as a acrylic pressure sensitive adhesive or any of theother adhesives described herein). A suitable acrylic pressure sensitiveadhesive includes Gelva 263 available from UCB Inc. which includes 8% byweight of benzophenone type UV absorber for light stability. Thepressure sensitive adhesive may be coated at a rate of 4 lbs. per reamcoat rate.

The film used to provide glass fragmentation protection should belocated on the glass surface of a window which is in the interior of thebuilding to prevent glass fragments from causing injury to occupants inthe building.

The invention encompasses an improved combination of filters whichprovides high visible light transmission and low electrical resistance(less than 4 ohms/square) for enhanced attenuation of electromagneticinterference (EMI) and enhanced attenuation of radio frequencyinterference (RFI) as well as effective filtering of UV and IR light.Some embodiments of the improved combination of filters provided by thisinvention are particularly useful for shields which are applied toplasma display screens and other display screens which emit largeamounts of EMI/RFI, UV light or IR light. The shields provide themonitor with a security feature which is useful for preventingunauthorized surveillance of the display screen.

The invention also provides for the selection of various combinations offilters to customize the anti-surveillance security features to suit aparticular need. This is because the combination of filters whichaffords the highest level of anti-surveillance security typicallyproduces light transmission characteristics which are not aestheticallypleasing when used on a window. Not everyone needs such a high level ofsecurity which would necessitate compromising visual aesthetics. Formany applications, e.g., business and home use, it may be desirable toprovide an acceptable level of security for many applications withoutcompromising visual aesthetics.

A combination of filters for filtering selected wavelengths ofelectromagnetic radiation is provided on a transparent substrate such asa plastic film or glazing of a window. The combination of filtersprevents or attenuates the passage of wavelengths through the substrateinto a building, where the passage of the wavelengths into the buildingcould adversely affect people or machinery within the building. Thecombination of filters is useful improve wireless networks performanceby blocking or attenuating undesired electromagnetic interference, andradio frequency interference.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description, serve to explain the principles of theinvention.

FIG. 1 is a cross-sectional view of a combination of three light filtersof the present invention connected to a substrate.

FIG. 2 is a cross-sectional view of an embodiment of the inventionwherein two light filters of the invention are connected to one side ofthe substrate and the third filter of the invention is attached toanother side of the substrate.

FIG. 3 is a cross-sectional view showing an embodiment of the inventionwhich utilizes a double glazed window.

FIG. 4 is a cross-sectional view of an embodiment of the invention whichincludes a plurality of light filters attached to conventional safetyglass.

FIG. 5 is a cross-sectional view of an embodiment of the inventionwherein sealant is used to cover any gaps between the edge of a flexiblesheet of the invention and a window frame.

FIGS. 6-8 are cross-sectional views of embodiments of the invention.

FIG. 9 is a cross-sectional view of the embodiments of the inventionwhich includes a temporary release liner.

FIG. 10 is a cross sectional view of the embodiments of the inventionwherein the combination of light filters are adhered to a window orother surface after removal of a release liner.

FIG. 11 is a graph which shows the light transmission properties(wavelengths from 300-400 nm) of a light filter used in the presentinvention.

FIG. 12 is a cross-sectional view of an embodiment of the inventionwherein the filter combination is embedded within PVB layers which areinterposed between multiple glass layers.

FIG. 13 is a top view of the embodiment depicted in FIG. 12.

FIG. 14 is a cross-sectional view of the embodiment of the inventionwhich employs a glass-fragmentation safety shield as a componentthereof.

FIG. 15 is a cross-sectional view of an embodiment of the inventionwhich includes two spaced apart filter combinations.

FIG. 16. depicts the use of the film layers to prevent unwanted emissionfrom entering an enclosure in accordance with embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

As noted above, the light filters may be sequenced or distributed in anymanner. FIG. 1 illustrates an embodiment wherein film layers 1, 2 and 3(which are light filters used in the present invention) are connected toone side of substrate 4.

FIG. 2 illustrates an alternative embodiment wherein film layers 1 and 2are connected to one side of the substrate 4 while film layer 3 isconnected to the other side of substrate 4. In a further embodimentillustrated in FIG. 3, the window glazing which serves as the substratecomprises two separate spaced-apart glass sheets 5 and 6. Film layers 1and 2 are attached to either side of glass sheet 5 while film layer 3 isattached to glass sheet 6. Film layer 3 in FIG. 3 may be attached toeither side of sheet 6. In a further embodiment illustrated in FIG. 4,the substrate upon which the films are connected may be a standardsafety glass which includes PVB interlayer 7 interposed between glasssheets 5 and 6. Film layers 3 and 2 are connected to glass sheet 5 andfilm layer 1 is connected to glass sheet 6. It is also possible toconnect any or all of film layers 1, 2 and 3 to PVB interlayer 7.

The above described versatility concerning the sequence and distributionof a combination of three light filters used in the present invention isalso applicable to other embodiments of the invention which use less ormore than 3 light filters in the combination.

One of the light filters of the combination may be a metal or a metalstack comprising an electrically conductive metal layer which isoptionally interposed between two nickel/chrome alloy layers. Theelectrically conductive metal layer preferably has at least theelectrical conductivity of aluminum or higher, and more preferably hasat least the electrical conductivity of copper or higher. Mostpreferably the electrically conductive metal is copper. The nickelchrome alloy is utilized to provide corrosion protection for theelectrically conductive metal and may be omitted if the anti-corrosionbenefit is not desired. Other anti-corrosion metals or metal alloys suchas stainless steel may be substituted for one or both the nickel/chromealloy layers. It is also possible to provide the nickel/chrome alloy oran anti-corrosion metal or metal alloy on only one side of theelectrically conductive metal layer. The nickel/chrome alloy layers mayinclude a Hastelloy alloy or an Inconel alloy, which are well known tothose skilled in the art. An example of a Hastelloy alloy includesHastelloy C276, which has the characteristics shown in Table 1: TABLE 1Chemical composition, percent by weight: C, 0.02^(a), Mn, 1.00^(a); Fe,5.50; S, 0.03^(a); Si, 0.05^(a); Cr, 15.50; Ni, balance; Co, 2.50^(a);Mo, 16.00; W, 3.75; V, 0.35^(a); P, 0.03^(a) Maximum Physical constantsand thermal properties Density, lb/in.³: 0.321 Coefficient of thermalexpansion, (70-200° F.) in./in./° F. × 10⁻⁶: 6.2 Modus of elasticity,psi: tension, 29.8 × 10⁶ Melting range, ° F.: 2,415-2,500Specific heat,Btu/lb/° F., 70° F.: 0.102 Thermal conductivity, Btu/ft2/hr/in./° F.,70° F.: 69 Electrical resistivity, ohms/cmil/ft, 70° F.: 779 HeatTreatments Solution heat treat 2,100° F., rapid quench. TENSILEPROPERTIES Solution Treated 2,100° F., Water Quench Y.S., psi, Elong.,in 2 Hardness, Temperature, ° F. T.S., psi 0.2% offset in. % Brinell  70 113,500  52,000 70 —   400 101,700  44,100 71 —   600 95,100 39,10071 —   800 93,800 33,500 75 — 1,000 89,600 31,700 74 — 1,200 86,90032,900 73 — 1,400 80,700 30,900 78 — 1,600 63,500 29,900 92 — 1,80039,000 27,000 127  — Rupture Strength, 1,000 hr Solution Treated, 2,100°F., Water Quench Test Temperature, Strength, Elong., Reduction ° F. psiin 2 in., % of area, % 1,200 40,000 — — 1,400 18,000 — — 1,600  7,000 —— 1,800  3,100 — — Impact Strength Solution Treated, 2,100° F., WaterQuench Test temperature, Strength, ° F. Type test ft-lb −320Charpy-V-notched 181  +70 Charpy-V-notched 238 +392 Charpy-V-notched 239

An example of an Inconel alloy includes Inconel 600 which has thecharacteristics shown in table 2. TABLE 2 Chemical composition, percentby weight: C, 0.08; Mn, 0.5; Fe, 8.0; S, 0.008; Si, 0.25; Cr, 15.5; Ni,76.0 Cu, 0.25; Ti, 0.35; Al, 0.25 Physical constants and thermalproperties Density, lb/in.³: 0.304 Coefficient of thermal expansion,(70-200° F.) in./in./° F. × 10⁻⁶: 7.4 Modulus of elasticity, psi:tension, 30 × 10⁶; torsion, 11 × 10⁶ Poisson's ratio: 0.29 Meltingrange, ° F.: 2,470-2,575 Specific heat, Btu/lb/° F., 70° F.: 0.106Thermal conductivity, Btu/Ft²/hr/in./° F., 70° F.: 1 Electricalresistivity, ohms/cmil/ft, 70° F.: 620 Curie temperature, ° F.:annealed, −192 Permeability (70° F., 200 Oe): annealed, 1.010 Heattreatments used in annealed condition, 1,850° F./30 min. TensileProperties Hot Rolled Y.S., psi, 0.2 Elong. in 2 Hardness, Temperature,° T.S., psi offset in. % Brinell 70 90,500 36,500 47 — 600 90,500 31,10046 — 800 88,500 29,500 49 — 1,000 84,000 28,500 47 — 1,200 65,000 26,50039 — 1,400 27,500 17,000 46 — 1,600 15,000 9,000 80 — 1,800 7,500 4,000118 — Rupture Strength, 1,000 hr Solution Annealed, 2,050° F./2 hr TestTemperature, Elong., in 2 in., Reduction of ° F. Strength, psi % area, %1,500 5,600 — — 1,600 3,500 — — 1,800 1,800 — — 2,000 920 — — CreepStrength (Stress, psi, to Produce 1% Creep) Solution Annealed 2,050°F./2 hr. Test Temperature, ° F. 10,000 hr 100,000 hr 1,300 5,000 — 1,5003,200 — 1,600 2,000 — 1,700 1,100 — 1,800 560 — 2,000 270 — FatigueStrength Annealed Test temperature, ° F. Stress, psi Cycles to failure70 39,000 108 Impact Strength Annealed Test temperature, ° F. Type testStrength, ft-lb +70 Charpy-V-notched 180 800 Charpy-V-notched 187 1,000Charpy-V-notched 160

Another light filter which may be used in this invention includes a heatreflecting film. The heat reflecting film may be a sputtered metal/oxidestack described in U.S. Pat. No. 6,007,901 on a polyester (PET) filmwith UV absorbers dyed into it at 2.4 absorbance manufactured by thedyeing process described in U.S. Pat. No. 6,221,112. The disclosures ofthe aforementioned U.S. Pat. Nos. 6,007,901 and 6,221,112 areincorporated herein by reference. Alternatively any of the heatreflecting metal/oxide stacks described herein may be coated onto anycomponent of window glazing to thereby eliminate the need of a plasticfilm. In other words the metal/oxide stack may be deposited onto anycomponent of window glazing (e.g., coated directly or indirectly ontothe glass of window glazing) without first coating the metal/oxide stackonto a film (e.g., polyester film) and then adhering the metal/oxidecoated film onto the window glazing.

Any of the heat reflecting films which are well known to those skilledin the art may be used in this invention. Such heat reflecting filmsgenerally comprise multiple stacks of discrete layers which aredeposited onto a substrate such as a plastic film or glass. Each stackhas in sequence a thin film of dielectric material (e.g., metal oxide)and a heat reflecting metal such as silver, gold, copper or alloysthereof. Substantially transparent conductive metal compounds (e.g.,metal oxides) such as indium tin oxide may be used as the dielectric.

The heat reflecting film may comprise in sequence: (a) a substantiallytransparent substrate; (b) a first outer dielectric layer; (c) aninfrared reflecting metal layer; (d) a color correcting metal layercomprising a metal different from the infrared reflecting metal layer;(e) a protective metal layer comprising a metal different from theinfrared reflecting metal layer and different from the color correctinglayer; (f) one or more subcomposite layers each comprising: (i) asubcomposite inner dielectric layer; (ii) a subcomposite infraredreflecting metal layer; (iii) a subcomposite color correcting metallayer comprising a metal different from the subcomposite infraredreflecting metal layer; and (iv) a subcomposite protective metal layercomprising a metal different from the subcomposite infrared reflectingmetal layer and different from the subcomposite color correcting layer;and (g) a second outer dielectric layer.

The dielectric layers are typically indium oxide, indium zinc oxide,indium tin oxide or mixtures thereof. However other metal oxides may besubstituted for the above-mentioned oxides. Suitable oxides for use asthe dielectric layer include metal oxides having an index of refractionin the range of 1.7-2.6. The thickness of the outside dielectric layersis typically between about 0.15 quarter wave optical thickness and about1 quarter wave optical thickness.

The infrared reflecting metal layers are typically silver, gold, copperor alloys thereof and are laid down in a thickness of between 7 nm andabout 25 nm. The color correcting metal layers preferably have arefractive index between about 0.6 and about 4 and an extinctioncoefficient for light in the visible range between about 1.5 and about7. The color correcting metal layers most preferably consist essentiallyof indium.

The protective metal layers are made from a metal whose oxide issubstantially-optically non-absorbing, such as aluminum, titanium,zirconium, niobium, hafnium, tantalum, tungsten and alloys thereof. Theprotective metal layers typically have a thickness between about 1 nmand about 5 nm.

The heat reflecting film may also be a composite comprising in sequence:(a) a substantially transparent substrate; (b) a first outer dielectriclayer; (c) an infrared reflecting metal layer; (d) a color correctingmetal layer comprising a metal different from the infrared reflectingmetal layer; (e) a protective metal layer comprising a metal differentfrom the infrared reflecting metal layer and different from the colorcorrecting layer; (f) a second outer dielectric layer; and (g) asubstantially transparent top layer comprising a substantiallytransparent glass or polymeric material.

The heat reflecting film may also be a composite comprising in sequence:(a) a substantially transparent substrate; (b) a first outer dielectriclayer chosen from the group of dielectric materials consisting of indiumoxide, indium zinc oxide, indium tin oxide and mixtures thereof; (c) aninfrared reflecting metal layer comprising an alloy of silver andcopper; (d) a color correcting metal layer consisting essentially ofindium; (e) a protective metal layer comprising a metal whose oxide hasa heat of formation less than (more negative than) −100,000 cal/gm moleat 25 degree. C.; and (f) a second outer dielectric layer chosen fromthe group of dielectric materials consisting of indium oxide, indiumzinc oxide, indium tin oxide and mixtures thereof.

Preferably the various layers of the heat reflecting film are assembledso as to transmit between about 40% and about 80% of light within thevisible spectrum (preferably 40-60%). It is also preferable that thecomposites of the heat reflecting film have reflectances of visiblelight less than 15%, typically between about 5% and 15%. Finally, it ispreferable that the layers of the heat reflecting film be so assembledso that the composite transmits and reflects visible light in “neutralcolors” or “slightly blueish or greenish” transmission colors.Transmissions which are neutral in color are those which transmitvisible light in equal intensities throughout the visible spectrum.Light transmitted with a slightly blueish or slightly greenish tint islight whose components with wave lengths in the 380-580 nm range areslightly higher in intensity than other wave lengths.

According to one embodiment the heat reflecting film comprises insequence: a) a substantially transparent first substrate; (b) a firstouter dielectric layer; (c) an infrared reflecting metal layer; (d) acolor correcting metal layer comprising a metal different from theinfrared reflecting metal layer; (e) a protective metal layer comprisinga metal different from the infrared reflecting metal layer and differentfrom the color correcting layer; (f) a subcomposite comprising: (i) asubcomposite inner dielectric layer; (ii) a subcomposite infraredreflecting metal layer; (iii) a subcomposite color correcting metallayer comprising a metal different from the subcomposite infraredreflecting metal layer; and (iv) a subcomposite protective metal layercomprising a metal different from the subcomposite infrared reflectingmetal layer and different from the subcomposite color correcting layer;(g) a second outer dielectric layer; and (h) a substantially transparentsecond substrate; wherein the heat reflective filter transmits 40-80% oflight within the visible wavelengths (preferably 60-70%) and has areflectance of less than 15%; and wherein the color of both transmittedand reflected light from the heat reflecting fenestration product iseither neutral or is slightly blueish or slightly greenish in color.

In another embodiment the heat reflecting composite comprises insequence: (a) a substantially transparent first substrate; (b) a firstouter dielectric layer; (c) an infrared reflecting metal layercomprising silver; (d) a color correcting metal layer comprising a metalchosen from the group of metals consisting of chromium, cobalt, nickel,zinc, palladium, indium, tin, antimony, platinum, bismuth and alloysthereof; (e) a protective metal layer comprising a metal chosen from thegroup of metals consisting of aluminum, titanium, zirconium, niobium,hafnium, tantalum, tungsten and alloys thereof; (f) a subcompositecomprising: (i) a subcomposite inner dielectric layer; (ii) asubcomposite infrared reflecting metal layer comprising silver; (iii) asubcomposite color correcting metal layer comprising a metal chosen fromthe group of metals consisting of chromium, cobalt, nickel, zinc,palladium, indium, tin, antimony, platinum, bismuth and alloys thereof;(iv) a subcomposite protective metal layer comprising a metal chosenfrom the group of metals consisting of aluminum, titanium, zirconium,niobium, hafnium, tantalum, tungsten and alloys thereof; (g) a secondouter dielectric layer; and (h) a substantially transparent secondsubstrate disposed contiguous with the second outer dielectric layer;wherein the dielectric layers are chosen from the group of dielectricmaterials consisting of indium oxide, indium zinc oxide, indium tinoxide and mixtures thereof; wherein the heat reflective filter transmits40-80% of light within the visible wavelengths (preferably 60-70%) andhas a reflectance of less than 15%; wherein the color of bothtransmitted and reflected light from the heat reflect substrate iseither neutral or is blue or green in color; and wherein the compositetransmits less than about 7% of the infrared energy in light having awavelength greater than about 1500 nm.

In another embodiment the heat reflecting film is a composite comprisingin sequence: (a) a substantially transparent substrate; (b) a firstouter dielectric layer; (c) an infrared reflecting metal layer; (d) acolor correcting metal layer comprising a metal different from theinfrared reflecting metal layer; (e) a protective metal layer comprisinga metal different from the infrared reflecting metal layer and differentfrom the color correcting layer; (f) a subcomposite comprising: (i) asubcomposite inner dielectric layer; (ii) a subcomposite infraredreflecting metal layer; (iii) a subcomposite color correcting metallayer comprising a metal different from the subcomposite infraredreflecting metal layer; and (iv) a subcomposite protective metal layercomprising a metal different from the subcomposite infrared reflectingmetal layer and different from the subcomposite color correcting layer;and (g) a second outer dielectric layer; wherein the combined thicknessT₁ of the infrared reflecting metal layer, the color correcting metallayer and the protecting metal layer is different than the combinedthickness T₂ of the subcomposite infrared reflecting metal layer, thesubcomposite color correcting metal layer and the subcompositeprotecting metal layer, and wherein T₁ and T₂ are in a ratio to oneanother of about 1.2.

A preferred heat reflector film for use in this invention is made bysputter coating the following sequence of layers onto a PET film with UVabsorbers dyed into it at 2.4 absorbance: a first layer of indium tinoxide about 30 nm thick coated on said PET film, a first layer ofsilver/copper alloy about 9 nm thick (92.5 wt. % Ag and 7.5 wt. % Cu)coated on said first layer of indium tin oxide, a layer of indium metalabout 3 nm thick coated on said first silver/copper alloy, a first layerof titanium metal about 1 nm thick coated on said indium, a layer ofindium tin oxide about 80 nm thick coated on said titanium, a secondlayer of silver/copper alloy about 9 nm thick (92.5 wt. % Ag and 7.5 wt.% Cu) coated on said indium tin oxide, a layer of indium metal about 2nm thick coated on said second silver/copper alloy, a second layer oftitanium metal about 1 nm thick coated on said 2 nm layer of indium, anda second layer of indium tin oxide about 30 nm thick coated on saidsecond layer of titanium.

The layer of titanium functions as a protective sacrificial layer whichprevents oxidation of the indium metal layer during the sputter coatingof the indium tin oxide layer.

Alternatively the PET film may be eliminated and the above sequence oflayers may be coated onto a component (e.g., glass) of window glazing.

The above preferred heat reflector has a sheet resistance which is lessthan 17 ohms/square.

Some embodiments of the invention utilize the metal or metal stack whichcomprises an electrically conductive metal such as copper optionallyinterposed between the two nickel/chrome layers as well as the heatreflecting sputtered metal/oxide stack.

When both of these filters are employed, they may be replaced by afilter having the electromagnetic filtering properties of the XIR-70film or the XIR-75 film shown in table 3. The XIR-70 and XIR-75 filmshave an IR transmission at wavelengths between 780 nm and 2500 nm of nomore than 50%, and preferably of less than 20%, and more preferably ofabout 15%. XIR-70 and XIR 75 films are commercially available fromSouthwall Technologies. XIR-70 film and the XIR-75 films are well knowncomponents of glass tint used in original equipment laminated automotiveglass. Table 3 shows the characteristics of this type of tinted glassand, more particularly, table 3 shows the properties of XIR-70 film andXIR-75 film which may be used in the present invention as part of theoverall combination of filters. An example of the XIR film may be about2 mil. thick; have a visible light transmittance of about 60-70%, avisible reflectance (exterior) of about 9%; a total solar transmittanceof about 46%; and a solar reflectance (exterior) of about 22%. Thesurface resistance of an exemplitive XIR-70 film used in this inventionis about 6.0 ohms/square.

Preferably the XIR-70 or XIR-75 film further includes an electricallyconductive metal layer (e.g., copper or silver) to produce a sheetresistance which is less than 4 ohms/square. TABLE 3 Visible TotalRelative Product/ Unit Light Visible Solar Solar Heat Gain GlassThickness Transmittance Reflectance Transmittance Reflectance Btu's/Hr/Ultraviolet Type Si (Tvis) % Exterior % (Tsol) % Exterior % Ft² Blockage% Clear 4 mil 90 9 81 8 220 30 Glass Standard 4 mil 81 8 56 6 171 55Auto Green Tint Spectrally 4 mil 74 7 44 5 150 70 Absorbing Green XIR 705 mil 70 9 46 22 117 >99 XIR 75 5 mil 75 11 52 23 135 >99Note:XIR Glass construction is two plies of 2.1 mil clear glass with XIR-pvbinterlayer.

In a preferred embodiment, an improved anti-surveillance devices andsystem may be obtained by replacing the aforementioned metal stack(nickel chrome alloy/copper/nickel chrome alloy) and the heat reflectingmetal/oxide stack with a high visible light transmission/low resistance(less than 4 ohms/square) filter in the combination of filters.

Most broadly the high visible light transmission/low resistance (lessthan 4 ohms/square) filter is a stack which is either an IR reflectingmetal layer sandwiched between two dielectric layers or a dielectriclayer sandwiched between two IR reflecting metal layers. The above-notedstack is coated onto a component of window glazing or onto a transparentplastic sheet such as PET.

The dielectric of each of the dielectric layers in the aforementionedstack has an index of refraction in the range of about 1.35 to about2.6. Preferably the dielectric is a metal oxide dielectric having anindex of refraction in the range of about 1.7 to about 2.6.

The above-described high visible light transmission/low resistance (lessthan 4 ohms/square) filter is preferably a Ag/Ti stack or a Ag/Au stackas described below.

The Ag/Ti stack may be a multilayered structure containing the followingsequence of layers coated (preferably sputter coated) onto a componentof window glazing or onto a transparent plastic sheet which ispreferably polyethylene terephthalate (PET): 1. a layer of indium tinoxide which is preferably 30 nm thick; 2. a silver IR reflecting layerwhich is preferably about 9 nm thick; 3. a protective sacrificial layerof titanium about 1 nm thick; 4. a layer of indium tin oxide which ispreferably about 70 nm thick; 5. a silver IR reflecting layer preferablyabout 9 nm thick; 6. a protective sacrificial layer of titaniumpreferably about 1 nm thick; 7. an indium tin oxide layer preferablyabout 70 nm thick; 8. a silver IR reflecting layer preferably about 9 nmthick; 9. a protective sacrificial layer of titanium preferably about 1nm thick; and 10. a layer of indium tin oxide preferably about 30 nmthick.

The indium tin oxide layers in the Ag/Ti stack has an index ofrefraction of about 2.0. The thickness of the silver layers may beadjusted to achieve the desired ohms per square for the above-describedmultilayered structure. The above-described multi-layered structure hasa sheet resistance which is less than 4 ohms per square.

Preferably the Ag/Ti stack has a sheet resistance which is less than 2.5ohms/square. An Ag/Ti stack having a sheet resistance less than 2.5ohms/square is exemplified by a stack containing the following sequenceof layers sputtered onto a component of window glazing or onto atransparent plastic sheet which is preferably PET: 1. a coating ofindium tin oxide about 30 nm thick; 2. a silver IR reflecting layerwhich is about 11 nm thick; 3. a protective sacrificial layer oftitanium about 1 nm thick; 4. a layer of indium tin oxide about 75 nmthick; 5. a silver IR reflecting layer which is about 13 nm thick; 6. aprotective sacrificial layer of titanium about 1 nm thick; 7. an indiumtin oxide layer about 70 nm thick; 8. a silver IR reflecting layer about11 nm thick; 9. a protective sacrificial layer of titanium about 1 nmthick; and 10. a layer of indium tin oxide which is about 30 nm thick.

The Ag/Ti stack having the lower sheet resistance of less than 2.5 ohmsper square provides lower electrical resistance, higher IR rejection atthe 800 and above nm range with a visible light transmission of 70%.Using the Ag/Ti stack having a sheet resistance which is less than 2.5ohms/square, results in a filter which is less dark, more conductive andwhich provides greater IR rejection compared to the filter containingthe nickel-chrome alloy/copper/nickel-chrome alloy layered structurewith the metal/oxide heat reflecting film.

The protective sacrificial layer of titanium will be oxidized to TiO₂when the indium tin oxide layers are deposited to thereby prevent theindium tin oxide layer from oxidizing the silver.

The layers used in the Ag/Ti and Ag/Au stack may be sputter coated usingany conventional sputter coating technique. For example the indium tinoxide layer in the Ag/Ti sputtered stack may be sputtered in an argonand oxygen environment and the metals in the Ag/Ti stack may bedeposited in a pure argon environment.

The above described Ag/Ti stack has a visible light transmission (VLT)of about 65-69% T₅₅₀ (i.e., percentage of VLT measured using lighthaving a wavelength of 550 nm).

The Ag/Au stack is also a multilayered structure coated (preferablysputter coated) onto a component of window glazing or onto a clearplastic sheet such as PET and preferably contains the following sequenceof layers: 1. A layer of indium tin oxide (ITO) preferably about 30 nmthick; 2. a silver IR reflecting layer preferably about 9 nm thick; 3. alayer of gold about 1 nm thick; 4. an ITO layer preferably about 70 nmthick; 5. a silver IR reflecting layer preferably about 9 nm thick; 6. alayer of gold preferably about 1 nm thick; 7. an ITO layer preferablyabout 70 nm thick; 8. a silver IR reflecting layer preferably about 9 nmthick; 9. a gold layer preferably about 1 nm thick; 10. an ITO layerpreferably about 30 nm thick.

The ITO layers in the above-described Ag/Au stack have a refractiveindex of about 2.0. The thickness of the silver layers may be varied toregulate the ohms per square for the above-described multilayeredstructure. The above-described multilayered structure has a sheetresistance which is less than 4 ohms per square.

The gold layers in the Ag/Au stack serve as a protective layer for thesilver, but unlike the corresponding Ti layers in the Ag/Ti stack, thegold layers are not oxidized.

The ITO may be sputtered in an argon and oxygen environment while themetals may be deposited in a pure argon environment.

In both of the above described Ag/Ti and Ag/Au stacks, layer 1 (thefirst ITO layer) is first sputter coated onto a component of windowglazing or onto the clear plastic sheet and the remaining layers 2-10are sequentially sputter coated in the order indicated above.

In both of the above described Ag/Ti and Ag/Au stacks, any or all of theindium tin oxide layers may be substituted with any dielectric layerhaving an index of refraction in the range of about 1.35 to about 2.6,preferably a metal oxide dielectric having an index of refraction in therange of about 1.7 to about 2.6.

Another filter which may be used in the combination of filters is an IRabsorbing filter which is a layer comprising an IR absorbing substancesuch as a layer of LaB₆ (lanthanum hexaboride) or other IR absorbingmaterial such as antimony tin oxide. A preferred IR absorbing filtercontains a combination of LaB₆ and antimony tin oxide. The IR absorbingmaterial is preferably in the form of nanoparticles incorporated into acoating material such as adhesive or hardcoat material. Nanoparticlesare particles having an average particle diameter of 200 nm or less,preferably less than 100 nm.

Examples of suitable IR absorbing filters include the IR absorbingfilters described in United States published patent application no. U.S.Ser. No. 2002/0090507 A1 and WO 02/41041 A2, the specifications of whichare incorporated herein by reference.

The IR absorbing filters described in WO 02/41041 A2 and U.S. Ser. No.2002/0090507 A1 are optically active film composites which include alayer of resin binder having a thickness of less than 6 microns and apencil hardness of at least 2H, preferably 3H, and include nanoparticlesof at least one metallic compound absorbing light having a wavelength inthe range of 1000-2500 nm and nanoparticles of a second metalliccompound which is an inorganic compound and which absorbs light having awavelength in the range of 700-1100 nm. Preferably the composite has avisible light transmission of at least 50% and a percent TSER of atleast 35%, and more preferably has a visible light transmission of atleast 70%. For a composite having a visible light transmission in therange of 50-60% the percent TSER may be between 50-65%.

Pencil hardness is measured according to ASTM D3363-92a.

Visible light transmission is calculated using CIE Standard Observer(CIE 1924 1931) and D65 Daylight.

The percent TSER is the percentage total solar energy rejection which iscalculated from optical and heat rejection properties of coated filmmeasured on a Varian Analytical Cary 5 Spectrophotometer in accordancewith ASTM E903-82, the absorption and transmission data being analyzedusing parameters described by Perry Moon in the Journal of the FranklinInstitute, Volume 230, pp. 583-618 (1940).

Preferably one metallic compound is antimony tin oxide (ATO), indium tinoxide (ITO), or tin oxide.

Preferably said one metallic compound is ATO and the layer contains30-60% by weight of ATO, preferably 50-60% by weight of ATO.

The second compound may be modified ITO as described in U.S. Pat. No.5,807,511 and/or at least one of a metal hexaboride taken from thelanthanum series of the periodic table. The preferred hexaborides areLa, Ce, Pr, Nd, Gb, Sm, and Eu with La being the most preferred option.The layer contains a maximum of 3% by weight of the second metalliccompound, preferably less than 2% and more preferably between 0.5-2%.

The binder may be a thermoplastic resin such as an acrylic resin, athermosetting resin such as an epoxy resin, an electron beam curingresin, or preferably a UV curable resin which may be an acrylate resinof the type disclosed in U.S. Pat. No. 4,557,980, or preferably aurethane acrylate resin.

The layer of resin binder may be coated to a transparent polymeric filmsubstrate, preferably a polyester film which is more preferably PETfilm. The infrared blocking layer forms a hardcoat for the filmsubstrate which is particularly advantageous and may cut out a furtherprocessing step during composite film manufacture. The PET film may becoated with an adhesive for fixing the film composite to the substrateused in this invention. The PET film and/or adhesive may include atleast one UV radiation absorbing material to block out substantially allUV radiation to less than 1% weighted UV transmission. Weighted UVtransmission is derived from measurements made in accordance with ASTME-424 and as modified by the Association of Industrial Metallisers,Coaters & Laminators (AIMCAL). The above-mentioned IR absorption filtercomposites have low visible reflectivity of less than 10% and haveexcellent weatherability with no loss of absorption properties andholding color, after 1500 hours in a Weatherometer.

The IR absorbing filter may include a transparent substrate coated witha layer of resin having a thickness of less than 6 microns and whichcontains nanoparticles of ATO and nanoparticles of a second metalliccompound which is an inorganic compound which absorbs light having awavelength in the range of 700-1100 nm and a second transparentsubstrate located on the layer of resin so that the layer of resin issandwiched between the two substrates.

Another filter which may be used in the combination of filters is a UVscreening film. The UV screening film is advantageously a weatherablePET UV screening film which is preferably a PET film with UV absorbersdyed into it in an amount to produce at least 2.4 optical density (OD)absorbance. A suitable PET film includes the film manufactured by thedyeing process described in U.S. Pat. No. 6,221,112. One or two of theUV screening films may be used in the present invention. Instead ofusing a UV screening film, the UV absorbers may be incorporated into oron a component of window glazing.

Conventional museum grade film comprises the combination of two layersof the aforementioned UV screening film. Thus, the museum grade film maybe substituted for any of the embodiments of this invention whichinclude two UV screening films in the overall combination of filters.

The museum grade film has the wavelength transmission properties of FIG.11. The museum grade film exhibits an increasing percentage of lighttransmission beginning about 380 nanometers as shown in FIG. 11. In oneembodiment, the museum grade film exhibits light transmissionpercentages for various wavelengths as shown below in table 4. TABLE 4Wavelength Light Transmission 320 nm 0.1-0.3% 380 nm 0.4-0.5% 400 nm   3-5% 550 nm   85-88%

A film having the properties shown in FIG. 11 and in table 4 may have apercent light transmission at 320 nm and 380 nm which is less that 1% ofthe transmission at 550 nm. In addition, the percent light transmissionat 480 nm may be less than 50% of the transmission at 550 nm.

A flexible transparent sheet made in accordance with this invention mayalso be used to minimize acoustic transmissions from a building bycarefully applying the film to the window with an adhesive while makingcertain that no visible air bubbles are formed between the flexiblesheet and the glazing of the window. The term “visible air bubbles” usedherein means air bubbles which are visible without any magnification(i.e., visible to the naked eye). It has been discovered that when thetransparent flexible sheet lies over an air bubble, the flexible sheetbehaves like the diaphragm of a loudspeaker. This causes unwantedtransmission of sound waves. Avoiding these bubbles minimizes thetransmission of the sound waves through the window.

The combination of filters used in this invention should cover thesurface area of the entire window glazing or otherwise should beconfigured to minimize the passage of the selected wavelengthsthere-through unless the combination of filters is being used as a bagor tent. Thus, when the filters are applied to the glazing by adhering aflexible transparent sheet thereto, the flexible transparent sheethaving the light filters thereon should be carefully positioned so thatthere are no gaps or unprotected areas on the glazing. In an embodiment,a single transparent flexible sheet having the filters thereon isemployed to avoid seams between the edges of the flexible sheets on theglazing of a window. The avoidance of seams is beneficial because seamsallow leakage of the wavelengths which the present invention seeks toavoid. This leakage through the seams occurs even when the edges of theflexible sheets are butted against one Another and even when the edgesoverlap one another.

There is also a potential for leakage of the wavelengths around theperiphery of the flexible sheet adjacent to the window frame. Turning toFIG. 5, leakage around the periphery may be minimized by applying anopaque electrically conductive sealant 22 around the periphery so thatany gap 23 between the sheet 24 and the window frame 25 may be masked bythe sealant. Thus, the sealant would cover any exposed portions of theglazing not covered by the sheet. FIG. 5 illustrates sheet 24 adhered toglazing 26 of a standard window. The sealant may be neutral curing toavoid unwanted chemical interaction with the sheet. An example ofsuitable sealant includes a silicone elastomer, such as Dow Corning 995Silicone Structural Adhesive.

Preferably the flexible sheet is sized to avoid all gaps between sheet24 and window frame 25. However it is not humanly possible to avoid allgaps between sheet 24 and window frame 25 due to small irregularities onthe edges of sheet 24 and window frame 25. Thus sheet 24 should be sizedso that the entire periphery of sheet 24 is in substantial contact withwindow frame 25. Substantial contact as used herein means as muchcontact as is humanly possible given the small irregularities on theedges of sheet 24 and window frame 25.

A first combination of filters used in the present invention comprisesthe above described low resistant sputtered stack (either the Ag/Ti orthe Ag/Au stack or the stacks having the sequence: dielectric layer/IRreflecting metal layer/dielectric layer or the sequence: IR reflectingmetal layer/dielectric layer/IR reflecting metal layer) in combinationwith one or two UV screening films. An example of the first improvedcombination of filters is illustrated in FIG. 6.

Turning to FIG. 6, this embodiment of the invention includes layers27-32. Layer 27 is an adhesive for adhesively securing the multilayeredstructure to glazing of a window or to the display screen of a plasmamonitor or other type of display screen. Layer 28 is a UV screeningfilm. Layer 29 is either the Ag/Ti or the Ag/Au low resistance (lessthan 4 ohms/square, preferably less than 2.5 ohms per square) sputteredstack as described herein. Layer 30 is a laminating adhesive. Layer 31is either a clear film or a UV screening film. Layer 32 is an optionalhardcoat layer.

The above-described first combination offers high visible lighttransmission and high EMI/RFI shielding attenuation. Thus the firstcombination may be applied to glazing of a window using adhesive layer27 or may be adhered to the display screen of a plasma monitor or otherdisplay screen which emits large amounts of EMI/RFI, UV or IR.

The embodiment shown in FIG. 6 may be assembled using conventional filmmaking, coating and laminating procedures. For example Ag/Ti stack oflayer 29 is formed on film 28 by conventional sputtering and hardcoatlayer 32 is applied onto layer 31 using conventional hardcoatingtechniques either before or after lamination of the remaining layers.The entire multilayered structure is assembled into a laminate usingconventional laminating adhesives and adhesive layer 27 is applied usingconventional adhesive coating technology.

A second combination of filters comprises the above-described Ag/Ti orthe Ag/Au low resistance sputtered stack or the stacks having thesequence: dielectric layer/IR reflecting metal layer/dielectric layer orthe sequence: IR reflecting metal layer/dielectric layer/IR reflectingmetal layer, the above-described IR absorbing layer which preferablycomprises LaB₆ and antimony tin oxide, and one or two UV screeningfilms. An example of the second improved combination is illustrated inFIG. 7.

Turning to FIG. 7, this embodiment of the invention includes layers27-33. Layers 27-32 may be the same material as layers 27-32 of FIG. 6.Layer 33 in FIG. 7 is the aforementioned IR absorbing layer whichpreferably comprises LaB₆ and antimony tin oxide.

The second combination of filters such as the combination of filtersexemplified in FIG. 7 provides improved IR rejection at the near IRwavelength range due to the incorporation of layer 33 therein. Inaddition, the second combination provides high EMI/RFI shieldingattenuation and provides standard and high UV rejection. Standard UVrejection is provided by the embodiments of FIGS. 6 and 7 wherein layer31 is a clear film. Higher UV rejection is obtained when layer 31 is theUV screening film in the embodiment shown in FIGS. 6 and 7.

The example illustrated by FIG. 7 may be adhered to window glazing or toa plasma display screen or other type of display screen which emitslarge amounts of EMI/RFI or which emits large amounts of UV or IR light.

The embodiment shown in FIG. 7 may be assembled using the sameconventional film making, coating and laminating procedures as describedfor the embodiment of FIG. 6 but which further includes coating a layerof IR absorbing material (e.g., a layer comprising LaB₆ and antimony tinoxide) onto film 31.

A third combination of filters utilized in this invention comprises thepreviously described sputtered metal or metal stack (electricallyconductive metal such as copper optionally sandwiched between twocorrosion protection layers), a heat reflecting sputtered stack (thepreviously described sputtered metal/oxide stack) and the UV screeningmaterial of layer 28 used in the example illustrated in FIG. 6. Thethird improved combination of filters is exemplified in FIG. 8 whichincludes the sequence of layers 27, 28, 30, 36, 30, 37, 30, 31 and 32.Layers 27, 28, 30, 31 and 32 in FIG. 8 are the same material as thecorresponding numbered layers in the embodiment illustrated in FIG. 6.Layer 36 is the nickel/chrome alloy-copper-nickel/chrome alloy stackdescribed herein. Preferably the nickel/chrome alloy is Hastelloy C276alloy or the Inconel 600 alloy. Specific examples of Hastelloy C276 andInconel 600 are described below:

Hastelloy C276 having the following mechanical properties: UTI tensilpsi: 106,000; yield psi: 43,000; elong. % 71.0; and having the followingchemical analysis as shown in Table 5: TABLE 5 Hastelloy C 276 Element %by weight C .004 Fe 5.31 Mo 15.42 Mn 0.48 Co 1.70 Cr 15.40 Si .02 S .004P .005 W 3.39 V 0.16 Ni Balance

Inconel 600 having the following mechanical properties: UTI tensil psi:139,500; yield psi 60,900; elong. % 44.0; hardness: Rb85; and having thefollowing chemical analysis as shown in Table 6: TABLE 6 INCONEL 600element % by weight C .08 Fe 8.38 Ti 0.25 Mn 0.21 Cu 0.20 Co 0.05 Cr15.71 Si 0.30 S <.001 Al 0.28 P 0.01 Ni 74.45 Nb + Ta 0.08

Layer 37 is a heat reflecting film. The heat reflecting film of layer 37preferably includes a sputtered metal/oxide stack (described in U.S.Pat. No. 6,007,901) on a 1 mil. clear weatherable polyester (PET) film.The polyester film has UV absorbers dyed into it at at least 2.4 opticaldensity absorbance. The film may be dyed using the dyeing processdescribed in U.S. Pat. No. 6,221,112. Other films with UV screeningcapability may be used in place of the aforementioned UV screening film.

The embodiment shown in FIG. 8 is assembled using the same conventionaltechniques employed in making the embodiments of FIGS. 6 and 7. Inparticular, layer 36 is made by sputter coating the metal stack (copperlayer interposed between two nickel/chrome alloy layers) onto atransparent plastic film such as a 1 mil PET film. Layer 37 is formed bysputter coating the metal-oxide stack onto a 1 mil clear weatherable PETfilm with UV absorbers dyed into it to produce at least 2.4 opticaldensity absorbance. Layers 36 and 37 along with films 28 and 31 arelaminated together using the laminating adhesive layers 30, and adhesivelayer 27 is applied using conventional adhesive coating technology.Optional hardcoat layer 32 may be applied to film 31 using conventionalhardcoat coating techniques either before or after lamination of theremaining layers.

Each of the embodiments of the invention illustrated in FIGS. 6-8advantageously includes a temporary release liner which covers anexposed surface of adhesive layer 27. FIG. 9 illustrates the location ofrelease liner 38 secured to adhesive layer 27. Reference numeral 39 inFIG. 9 represents the various layers located below adhesive layer 27 inthe embodiments shown in FIGS. 6-8. Removal of release liner 38 exposesadhesive layer 27 and thereby allows the combination of filters to beadhesively secured to a desired substrate 40 such as the glazing of awindow or the screen of a computer monitor as illustrated in FIG. 10. Amechanical fastener may be used in place of an adhesive for securing thevarious embodiments of the invention to the screen of a computermonitor.

The release liner 38 used in the various embodiments of this inventionmay be any conventional release liner known to those skilled in the art.For example, the release liner may be a 1 mil PET film with a siliconerelease coating thereon. Any suitable silicone release coating may beused, such as a tin catalyzed silicone release which has about 10 gramsper inch release characteristic. Non-silicone release formulations maybe substituted for the silicone release layer.

The adhesive layer 27 used in the various embodiments of this inventionmay be any adhesive known to those skilled in the art for attaching aplastic sheet to glass. Pressure sensitive adhesives are particularlysuitable for this purpose. A non-pressure sensitive adhesive which maybe used is advantageously a clear distortion free adhesive such as afunctional polyester based adhesive having siloxane functionality whichprovides a strong bond to glass.

An example of a pressure sensitive adhesive includes an acrylic solventbased pressure sensitive adhesive which is applied at about 10 lb./reamcoat weight. The pressure sensitive adhesive of layer 27 may include 4%by weight of a UV absorber such as a benzotriazole UV absorber. Such apressure sensitive adhesive is commercially available as National Starch80-1057. Other adhesives or adhesive types may be substituted for thePSA adhesive as can other types of UV absorbers. It should beappreciated by one of ordinary skill in the art that these UV absorbersfunction as stabilizers, and may be added to the present invention toprotect the adhesive from deterioration (e.g., deterioration caused bysunlight). These stabilizers, however, are not required to practice theinvention.

The adhesive layer such as layer 27 may be omitted if the combination offilters is in the form of a flexible bag or a tent.

Layer 28 used in the various embodiments of this invention is aweatherable PET UV screening film which is preferably a PET film with UVabsorbers dyed into it at at least 2.4 optical density (OD) absorbance.A suitable PET film for layer 28 includes the film manufactured by thedyeing process described in U.S. Pat. No. 6,221,112. Other films withsimilar UV screening capability may be substituted for theabove-described film used in layer 28.

The thickness of the PET film used to make layer 28 may be varied. Forexample, the film used in layer 28 in FIGS. 6 and 7 is desirably 1 milthick to provide sufficient support for other layers used in the overallstructure. The thickness of layer 28 in FIG. 8 may be 0.5 mil thick.

The low resistance sputtered stack of layer 29 used in the variousembodiments of this invention may be either the Ag/Ti or the Ag/Au stackas described herein or a similar configuration on a PET clear substrate.The low resistance stack provides higher visible light transmission.

The laminating adhesive layer 30 used in the various embodiments of theinvention may be any conventional laminating adhesive including pressuresensitive adhesives known to those skilled in the art of thetechnological area of this invention. A useful laminating adhesiveincludes any conventional polyester adhesive with an isocyanatecross-linker added thereto. An example of such a laminating adhesive isRohm and Haas' Adcote 76R36 adhesive with catalyst 9H1H. The adhesivemay be applied at 1-1.5 lb. per ream coat weight. Other laminatingadhesives may be substituted for the above-noted polyester-typeadhesive.

Layer 31 used in the various embodiments of this invention is a clearplastic film such as clear PET which is optionally provided with a UVscreening capability as described above with respect to layer 28. Thus,the clear PET layer 31 is preferably a clear PET film which optionallyhas UV absorbers dyed into it at at least 2.4 OD absorbance. Thethickness of the PET film used in layer 31 may be varied. For example,the PET film used in layer 31 of FIGS. 6 and 8 may be 0.5 mil thick. ThePET of layer 31 in FIG. 7 may be 0.5 or 1 mil thick. Also, layer 31 inFIG. 8 is clear PET film without UV absorbers dyed into it. The PET oflayer 31 in FIGS. 6 and 7 may be either the clear PET without the UVabsorbers dyed into it or may be the clear PET with UV absorbers dyedinto it at at least 2.4 OD absorbance. The “2.4 absorbance” referred toherein is measured at 358 nm wavelength.

The hardcoat layer 32 used in the various embodiments of this inventionmay be formed from any of the hardcoat materials described herein orfrom any other conventional hardcoat material. Layer 32 used in thevarious embodiments of this invention is preferably 1-2 microns thick.The hardcoat is used to protect the combination of filters from damageand therefore the hardcoat may be omitted when the combination offilters is in a protected area where damage is not likely to occur. Asuitable hardcoat composition includes the hardcoat described in U.S.Pat. No. 4,557,980; the specification of which is incorporated herein byreference.

Layer 33 used in the various embodiments of this invention is theaforementioned IR absorbing layer which preferably comprises LaB₆ andantimony tin oxide as a coating or film.

Layer 36 used in the various embodiments of this invention may be a 1mil PET film or a functionally equivalent plastic film with a sputteredheat reflecting-conductive metal stack coating made up of a copper layerinterposed between two nickel/chrome alloy layers. Layer 36 has avisible light transmission of about 35%. The nickel/chrome alloy layersare preferably Hastelloy C276 or Inconel 600. Layer 36 which includesthe film with the metal stack deposited thereon, preferably has a sheetresistance which is less than 8 ohms per square.

Layer 37 used in the various embodiments of this invention is a heatreflecting film which preferably includes the above-described sputteredmetal/oxide stack (described in U.S. Pat. No. 6,007,901) on a 1 milclear weatherable polyester (PET) film. The polyester film has UVabsorbers dyed into it at at least 2.4 OD UV absorbance (2.4 OD UVabsorbing PET). The film may be dyed using the dyeing process describedin U.S. Pat. No. 6,221,112. Other films with similar UV screeningcapability may be used in place of the aforementioned UV screening film.

According to a preferred embodiment, two spaced apart filtercombinations are utilized in combination with a window glazing unit toprovide enhanced security. For example, a film comprising a combinationof filters may be adhered to each side of a glazing unit (e.g., glass orplastic glazing) or one film comprising a combination of filters may beadhered to each of two spaced apart transparent sheets of a glazingunit. Alternatively, two spaced apart films each of which comprises acombination of filters may be spaced apart within the space locatedbetween two spaced apart transparent sheets of a glazing unit.

In a preferred embodiment of the spaced apart filter combinations, eachof the filter combinations are embedded. (preferably completelyembedded) within a PVB interlayer of a glazing unit which includes atleast one PVB layer interposed between two transparent sheets of glazingmaterial (e.g., glass or plastic). More preferably one filtercombination is embedded in a first PVB interlayer and another filtercombination is embedded in a second PVB interlayer spaced apart from thefirst PVB interlayer. An example of this more preferred embodiment isillustrated in FIGS. 12 and 13.

The embodiment depicted in FIG. 12 includes front and rear surfaces 49and 50, glass layers 41, 42 and 43 with PVB interlayer 44 interposedbetween glass layers 41 and 42 and PVB interlayer 45 interposed betweenglass layers 42 and 43. The PVB layers 44 and 45 fill the gap betweenthe glass sheets and include films 47 and 48 embedded therein. Films 47and 48 comprise any of the above-described filter combinations as acomponent thereof. Preferably each edge 46 of films 47 and 48 lie withinthe PVB so that the edges are not exposed to water, oxygen or othercorrosive or harmful environmental conditions. The edges, being embeddedwithin the PVB interlayer, thereby produce a “picture frame”configuration as shown in FIG. 13 wherein the edge 46 of film 47 (andlikewise edge 46 of film 48) is spaced apart from the edge 51 of theentire structure.

The PVB layers are conventionally used in window manufacturing and serveto adhere the glass sheets to form a laminate which functions as asafety glass. The PVB layers used in this invention may be substitutedwith other similar plastic laminating layers such as polyurethane. Thepreferred glass layers may be substituted with other window glazingmaterials such as polycarbonate and polyacrylics. Thus the embodimentdepicted in FIG. 12 may use alternating layers of glass, polycarbonateand polyacrylic instead of the three glass layers.

Another embodiment of the invention which utilizes two spaced apartfilter combinations is illustrated in FIG. 15. The embodiment shown inFIG. 15 is glazing for a window and includes therein two spaced apartfilms 47 and 48 which comprise any of the filter combinations describedherein. Layer 54 adhesively secures film 47 to film 48. Layer 54 may bea conventional safety glass interlayer such as PVB or the like.Alternatively layer 54 may be an adhesive layer. An adhesive layer isadvantageously used in place of the PVB for layer 54 in situations wherethe spacing between films 47 and 48 is smaller than the smallest spacingwhich would be permitted when PVB is used to adhesively secure films 47and 48. This is because PVB generally requires a relatively thickapplication to form layer 54 whereas adhesives can be applied in thinlayers to produce a narrow spacing between films 47 and 48 and thethickness of the adhesive can be adjusted to regulate the spacing.

The PVB or adhesive of interlayer 54 may be electrically conductive.Electrical conductivity may be achieved by any known technique such asby the incorporation of electrically conductive particles therein.

The embodiment shown in FIG. 15 also includes conventional interlayers55 and 56 made of PVB or the like and glass sheets 57 and 58 on theouter surfaces thereof.

FIG. 14 depicts an embodiment of the invention which includes a glasssubstrate connected to any of the filter combinations of the inventionwith a glass fragmentation safety film adhered thereto. In FIG. 14reference numeral 52 represents the combination of a glass substrateconnected to any of the filter combinations of the invention andreference numeral 53 represents a flexible plastic film such as PET filmadhesively secured to the combination 52.

The embodiments described herein include instances where the filters orcombination of filters are applied onto a film such as a plastic filmwhich in turn is adhered to window glazing. However it is within thescope of this invention to omit the film or films used for any filter orcombination of filters and apply the filter or combination of filtersonto or within a component of window glazing.

As described above, the present invention provides various combinationsof films layers, such as layers 1, 2 and 3, in order to accomplishdesired selective filtering of various bands of electromagneticradiation. Specifically, it can be seen that embodiments of the presentinvention provides a combination of two or more filters connected to asubstrate, such as glass, to block the passage of selected bands ofelectromagnetic radiation. In other words, the films layer combinationsdisclosed in the present invention have a particular desired function ofpreventing unwanted electromagnetic emissions from exiting an enclosurewhile still allowing the passage of certain desired electromagneticradiations. As previously described, the disclosed film combinationshave particular application in anti-surveillance security for preventingor attenuating the passage of electromagnetic wavelengths which pose asecurity risk. Thus, a building may be secure from surveillance whilestill allowing natural light and other desired wavelengths to enter orexit the building. Furthermore, an existing building may be retrofittedthrough the use of specialized films layer combinations to make theexisting building more secure against surveillance without requiringextensive reconfiguration, such as the removal of windows and otherradiation portals.

In another embodiment of the present invention, a film having acombination of filtering layers may be used to selectively control theentrance of types of radiation into an enclosure. Referring now to FIG.16, a filtering film 61 is applied to a building 60 using varioustechniques. For example, as described above, the filtering film 61 maybe applied as needed using specialized conductive glazing or otheradhesives to the glass surfaces of the building 60. The filtering film61 comprises a combination of layers, such as those described above inFIG. 1-15 and the associated text, where the layers of the filteringfilm 61 are chosen as needed to block the entrance of undesired types ofradiations into the building 60.

In a preferred embodiment of the present invention, the filtering film61 is a combination of two or more filters connected to a substrate,such as glass. One of the filters screens UV light. Another filter inthe combination generally has (1) a heat reflecting component and anelectrically conductive metal component, (2) a component having an IRtransmission at wavelengths between 780 nm and 2500 nm of no more than50%, or (c) a component which has a sheet resistance of less than 4 ohmsper square and comprises a sequence of layers. These layers generallyinclude a combination of dielectric layer and IR reflecting metal layerswherein the dielectric of each dielectric layer has an index ofrefraction in the range of about 1.35 to 2.6. In this way, the filteringfilm blocks or attenuates UV, IR and radiowave radiation.

Referring again to FIG. 16, the filtering film 61 may be adapted asneeded to prevent the entrance of unwanted man-made radiation 62 such asradio waves from a transmission source 63 and to prevent the entrance ofunwanted ambient radiation 64 from a natural source such as the sun.

The blocking or attenuation of unwanted radiations 62 and 64 is verydesirable. From a general public health standpoint, the blocking orattenuation of the unwanted radiations 62 and 64 protects workers andoccupants of the building 60 from maladies associated with exposure tothe unwanted radiations. This consideration is becoming more importantin newer constructions methods, such as “green architecture.” A greenbuilding places a high priority on health, environmental and resourceconservation performance over its life-cycle. Green design emphasizes anumber of new environmental, resource and occupant health concernsincluding reducing human exposure to noxious materials and conservingenergy. To achieve these goals, green buildings are typically more opento the environment, such as using increased window surface areas toachieve greater ambient lighting and heating, as well as to create amore pleasant interior environment. While the new construction methodsallow greater entrance of desired radiation, the exposure of occupantsin the building 60 to unwanted radiation 62 and 64 also increase aswell, thereby posing potential exposure-related health risks to theseoccupants.

There are also practical considerations for preventing unwantedradiations 62 and 64 from entering the building 60 because theseunwanted radiations 62 and 64 have harmful effects to the building 60and the equipment contained in the building 60. For example, wirelesscomputer networks using radio waves are increasingly common, and thefunctioning of these networks is adversely effected by the unwanted RFIin the unwanted radiations 62 and 64. Similarly, other bands ofradiation, such as UV energy have adverse effects on equipment inbuilding 60.

As disclosed above, the various combinations of the films disclosed inthe present invention may be used in the filtering film 61 as needed toblock or attenuate the unwanted radiations 62 and 64 while stillallowing the transmission of visible light and other desired radiation,such as needed to accomplish desired benefits of the green architecture.Where needed, the composition of the filtering film 61 and theconnection method of the filtering film 61 to the building 60 may beadjusted as described herein to selectively admit various desiredradiation bandwidths.

The foregoing description of the preferred embodiments of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not by this detailed description, but rather by theclaims appended hereto. Many embodiments of the invention can be madewithout departing from the spirit and scope of the invention.

1. A method for preventing or attenuating the passage of unwantedelectromagnetic wavelengths into an enclosure, the enclosure comprisingat least one transparent area comprising a transparent substrate, themethod comprising the step of applying a combination of filters to saidsubstrate, said combination of filters comprising a first light filterand a second light filter which screens UV light, wherein said firstlight filter is: a light filter (a) comprising a heat reflecting layerand an electrically conductive metal layer, or a light filter (b) havingan IR transmission at wavelengths between 780 nm and 2500 nm of no morethan 50%, or a light filter (c) which has a sheet resistance of lessthan 4 ohms per square and comprises a sequence of layers: dielectriclayer/IR reflecting metal layer/dielectric layer; or IR reflecting metallayer/dielectric layer/IR reflecting metal layer, wherein said sequenceof layers is coated onto said substrate or onto a transparent plasticsheet; said apparatus optionally further including an IR absorbingfilter; said combination of filters being configured to prevent orattenuate the passage of said electromagnetic wavelengths through saidapparatus and said dielectric of each dielectric layer has an index ofrefraction in the range of about 1.35 to 2.6.
 2. The method of claim 1,wherein said electrically conductive metal layer of light filter (a) hasat least the electrical conductivity of aluminum; said dielectric ofeach dielectric layer of filter (c) is a metal oxide having an index ofrefraction in the range of about 1.7-2.6; and said IR reflecting metalis silver.
 3. The method of claim 2, wherein said electricallyconductive metal layer of light filter (a) is copper; and light filter(c) comprises an Ag/Ti sputtered stack or a Ag/Au sputtered stack,wherein: said Ag/Ti sputtered stack has a sheet resistance less than 4ohms/square and is made by sputter coating the following sequence oflayers onto said substrate or onto a transparent plastic sheet: 1) alayer of metal oxide, 2) a silver IR reflecting layer, 3) a protectivesacrificial layer of titanium, 4) a layer of metal oxide, 5) a silver IRreflecting layer, 6) a protective sacrificial layer of titanium, 7) ametal oxide layer, 8) a silver IR reflecting layer, 9) a protectivesacrificial layer of titanium, 10) a layer of metal oxide; said Ag/Ausputtered stack has a sheet resistance less than 4 ohms/square and ismade by sputter coating the following sequence of layers onto saidsubstrate or onto a transparent plastic sheet: 1) a layer of metaloxide, 2) a silver IR reflecting layer, 3) a layer of gold, 4) a layerof metal oxide, 5) a silver IR reflecting layer, 6) a layer of gold, 7)a layer of metal oxide, 8) a silver IR reflecting layer, 9) a goldlayer, and 10) a layer of metal oxide.
 4. The method of claim 3, whereinsaid heat reflecting layer comprises a plurality of heat reflectingmetal layers and a plurality of dielectric layers; and, wherein: saidlight filter (b) has a sheet resistance less than 4 ohms/square andcomprises a film which exhibits a visible light transmittance of about60-70% a visible reflectance of about 9%, a total solar transmittance ofabout 46% and a solar reflectance of about 22%; and, wherein: saidsequence of layers of said sputtered Ag/Ti stack is made by coating thefollowing sequence of layers onto said transparent plastic sheet: 1) alayer of indium tin oxide about 30 nm thick, 2) a silver IR reflectinglayer about 9 nm thick, 3) a protective sacrificial layer of titaniumabout 1 nm thick, 4) a layer of indium tin oxide about 70 nm thick, 5) asilver IR reflecting layer about 9 nm thick, 6) a protective sacrificiallayer of titanium about 1 nm thick, 7) an indium tin oxide layer about70 nm thick, 8) a silver IR reflecting layer about 9 nm thick, 9) aprotective sacrificial layer of titanium about 1 nm thick, and 10) alayer of indium tin oxide about 30 nm thick; and, wherein: said sequenceof layers of said sputtered Ag/Au comprises the following sequence oflayers coated onto said transparent plastic sheet: 1) a layer of indiumtin oxide about 30 nm thick, 2) a silver IR reflecting layer about 9 nmthick, 3) a layer of gold about 1 nm thick, 4) an ITO layer about 70 nmthick, 5) a silver IR reflecting layer about 9 nm thick, 6) a layer ofgold about 1 nm thick, 7) an ITO layer about 70 nm thick, 8) a silver IRreflecting layer about 9 nm thick, 9) a gold layer about 1 nm thick, and10) an ITO layer about 30 nm thick; and, wherein: said second lightfilter comprises one or two PET films with UV absorbers dyed therein inan amount to produce at least 2.4 optical density absorbance in each PETfilm; and, wherein: said copper layer is sandwiched between twocorrosion protection metal or metal alloy layers which protect saidcopper layer from corrosion.
 5. The method of claim 3, wherein saidfirst light filter is said Ag/Ti sputtered stack or said Ag/Au sputteredstack and said second light filter comprises one or two PET films withUV absorbers dyed therein in an amount to produce at least 2.4 opticaldensity absorbance in each PET film.
 6. The method of claim 3, whereinsaid first light filter is light filter (a) comprising said heatreflecting layer and said copper layer is interposed between twonickel/chrome alloy layers; and said second light filter comprises oneor two PET films with UV absorbers dyed therein in an amount to produceat least 2.4 optical density absorbance in each PET film.
 7. The methodof claim 6, wherein said second light filter comprises two of said PETfilms with said UV absorbers dyed therein.
 8. The method of claim 7,wherein said heat reflecting layer is a film made by sputter coating thefollowing sequence of layers onto a PET film with UV absorbers dyedtherein to produce at least 2.4 optical density absorbance: 1) a layerof indium tin oxide about 30 nm thick, 2) a layer of Ag/Cu alloy about 9nm thick, 3) a layer of indium metal about 3 nm thick, 4) a layer oftitanium metal about 1 nm thick, 5) a layer of indium tin oxide about 80nm thick, 6) a layer of Ag/Cu alloy about 9 nm thick, 7) a layer ofindium metal about 2 nm thick, 8) a layer of titanium metal about 1 nmthick, and 9) a layer of indium tin oxide about 30 nm thick.
 9. Themethod of claim 3, wherein said substrate is configured as a tent. 10.The method of claim 3, wherein said substrate is configured as a bag.11. The method of claim 4, wherein said heat reflecting layer is a filmmade by sputter coating the following sequence of layers onto atransparent plastic film with UV absorbers dyed therein at 2.4 opticaldensity absorbance: 1) a layer of indium tin oxide about 30 nm thick, 2)a layer of Ag/Cu alloy about 9 nm thick, 3) a layer of indium metalabout 3 nm thick, 4) a layer of titanium metal about 1 nm thick, 5) alayer of indium tin oxide about 80 nm thick, 6) a layer of Ag/Cu alloyabout 9 nm thick, 7) a layer of indium metal about 2 nm thick, 8) alayer of titanium metal about 1 nm thick, and 9) a layer of indium tinoxide about 30 nm thick.
 12. The method of claim 4, wherein said firstlight filter is said Ag/Ti stack.
 13. The method of claim 12, whereinsaid combination of filters further comprises said IR absorbing filteras an additional light filter, wherein said IR absorbing filter is alayer which comprises LaB₆ and antimony tin oxide.
 14. The method ofclaim 4, wherein said second light filter comprises two of said PETfilms with said UV absorbers dyed therein.
 15. The method of claim 14,wherein said second light filter has the wavelength transmissionproperties of FIG.
 11. 16. The method of claim 15, wherein said secondlight filter has a wavelength light transmission at a wavelength of 320nm of substantially 0.1% to 0.3%, a wavelength light transmission at awavelength of 380 nm of substantially 0.4% to 0.5%, a wavelength lighttransmission at a wavelength of 400 nm of substantially 3% to 5%, and awavelength light transmission at a wavelength of 550 nm of substantially85% to 88%.
 17. The method of claim 5, wherein said first light filteris said Ag/Ti sputtered stack, wherein said Ag/Ti sputtered stack has asheet resistance less than 2.5 ohms per square and is made by sputtercoating the following sequence of layers onto a transparent plasticsheet: 1) a layer of indium tin oxide about 30 nm thick, 2) a silver IRreflecting layer about 11 nm thick, 3) a protective sacrificial layer oftitanium about 1 nm thick, 4) a layer of indium tin oxide about 75 nmthick, 5) a silver IR reflecting layer about 13 nm thick, 6) aprotective sacrificial layer of titanium about 1 nm thick, 7) an indiumtin oxide layer about 70 nm thick, 8) a silver IR reflecting layer about11 nm thick, 9) a protective sacrificial layer of titanium about 1 nmthick, and 10) a layer of indium tin oxide about 30 nm thick.
 18. Themethod of claim 17, wherein said combination of filters furthercomprises said IR absorbing layer as an additional light filter, whereinsaid IR absorbing filter is a layer which comprises LaB₆ and antimonytin oxide.
 19. The method of claim 3, wherein said substrate comprises aflexible transparent sheet configured for attachment to glazing of awindow.
 20. The method of claim 19, wherein the transparent substratefurther comprises a window with said flexible transparent sheet adheredto glazing of said window.
 21. The method of claim 19, wherein saidflexible transparent sheet is adhered to said glazing of said windowwith an adhesive, wherein visible air bubbles are excluded between saidtransparent sheet and said glazing.
 22. The method of claim 3, whereinsaid substrate comprises glazing of a window.
 23. The method of claim22, wherein said combination of filters further comprises a safety filmadhered to said glazing.
 24. The method of claim 22, wherein saidcombination of filters further comprises a spaced apart combination offilters comprising a first and a second combinations of filters, saidfirst and said second combinations of filters being spaced apart fromeach other.
 25. The method of claim 24, wherein the first and saidsecond combinations of filters are adhered to each other by anelectrically conductive adhesive or an electrically conductive layer ofPVB.
 26. The method of claim 24, wherein each of the first and saidsecond combinations of filters is embedded in spaced apart layers ofpolyvinylbutyral, wherein each polyvinylbutyral layer is sandwichedbetween layers of glass or plastic window glazing.
 27. The method ofclaim 24, wherein said combination of filters comprises an upper layercomprising a first glass sheet joined to the first combination offilters by a layer of PVB; a lower layer comprising a second glass sheetjoined to the second combination of filters by a second layer of PVB;said first and second combination of filters being adhesively secured toeach other by a third layer of PVB or by an adhesive layer; said thirdlayer of PVB and said adhesive having a thickness which determines adistance between said spaced apart combination of filters.
 28. Themethod of claim 27, wherein said third layer of PVB or said adhesive iselectrically conductive.
 29. A method for reducing electromagneticinterference, and radio frequency interference within an enclosurehaving transparent areas, the method comprising the step of applying aoptically transparent filter to said transparent areas, said filtercomprising an electrically conductive metal layer, said combination offilters being configured to prevent or attenuate the passage of theelectromagnetic interference and radio frequency interference throughthe transparent areas.
 30. The method of claim 29, wherein the filter isattached to the transparent areas using an electrically conductiveadhesive.
 31. The method of claim 29, wherein said electricallyconductive metal layer of the filter has at least the electricalconductivity of aluminum.
 32. The method of claim 29, wherein the filtercomprises an IR reflecting metal layer and one or more dielectriclayers, each of said dielectric layers having an index of refraction ofsubstantially 1.35 to 2.6.
 33. The method of claim 32, whereindielectric layer comprises a metal oxide having an index of refractionof substantially 1.7-2.6 and, wherein the IR reflecting metal layercomprises silver.
 34. The method of claim 29, wherein said filtercomprises an Ag/Ti sputtered stack, wherein said Ag/Ti sputtered stackhas a sheet resistance less than 4 ohms/square.
 35. The method of claim34, wherein said Ag/Ti sputtered stack is made by sputter coating thefollowing sequence of layers onto said substrate or onto a transparentplastic sheet: 1) a layer of metal oxide, 2) a silver IR reflectinglayer, 3) a protective sacrificial layer of titanium, 4) a layer ofmetal oxide, 5) a silver IR reflecting layer, 6) a protectivesacrificial layer of titanium, 7) a metal oxide layer, 8) a silver IRreflecting layer, 9) a protective sacrificial layer of titanium, 10) alayer of metal oxide.
 36. The method of claim 34, wherein said Ag/Tisputtered stack is made by coating the following sequence of layers ontosaid transparent plastic sheet: 1) a layer of indium tin oxide about 30nm thick, 2) a silver IR reflecting layer about 9 nm thick, 3) aprotective sacrificial layer of titanium about 1 nm thick, 4) a layer ofindium tin oxide about 70 nm thick, 5) a silver IR reflecting layerabout 9 nm thick, 6) a protective sacrificial layer of titanium about 1nm thick, 7) an indium tin oxide layer about 70 nm thick, 8) a silver IRreflecting layer about 9 nm thick, 9) a protective sacrificial layer oftitanium about 1 nm thick, and 10) a layer of indium tin oxide about 30nm thick.
 37. The method of claim 29, wherein said filter comprises anAg/Au sputtered stack, wherein said Ag/Au sputtered stack has a sheetresistance less than 4 ohms/square.
 38. The method of claim 37, whereinsaid Ag/Au sputtered stack is made by sputter coating the followingsequence of layers onto said substrate or onto a transparent plasticsheet: 1) a layer of metal oxide, 2) a silver IR reflecting layer, 3) alayer of gold, 4) a layer of metal oxide, 5) a silver IR reflectinglayer, 6) a layer of gold, 7) a layer of metal oxide, 8) a silver IRreflecting layer, 9) a gold layer, and 10) a layer of metal oxide. 39.The method of claim 37, wherein said Ag/Au sputtered stack comprises thefollowing sequence of layers coated onto said transparent plasticsheet: 1) a layer of indium tin oxide about 30 nm thick, 2) a silver IRreflecting layer about 9 nm thick, 3) a layer of gold about 1 nm thick,4) an ITO layer about 70 nm thick, 5) a silver IR reflecting layer about9 nm thick, 6) a layer of gold about 1 nm thick, 7) an ITO layer about70 nm thick, 8) a silver IR reflecting layer about 9 nm thick, 9) a goldlayer about 1 nm thick, and 10) an ITO layer about 30 nm thick; and,wherein: said second light filter comprises one or two PET films with UVabsorbers dyed therein in an amount to produce at least 2.4 opticaldensity absorbance in each PET film; and, wherein: said copper layer issandwiched between two corrosion protection metal or metal alloy layerswhich protect said copper layer from corrosion.
 40. The method of claim29, wherein said filter comprises a film made by sputter coating thefollowing sequence of layers onto a transparent plastic film with UVabsorbers dyed therein at 2.4 optical density absorbance: 1) a layer ofindium tin oxide about 30 nm thick, 2) a layer of Ag/Cu alloy about 9 nmthick, 3) a layer of indium metal about 3 nm thick, 4) a layer oftitanium metal about 1 nm thick, 5) a layer of indium tin oxide about 80nm thick, 6) a layer of Ag/Cu alloy about 9 nm thick, 7) a layer ofindium metal about 2 nm thick, 8) a layer of titanium metal about 1 nmthick, and 9) a layer of indium tin oxide about 30 nm thick.